Flexible battery

ABSTRACT

A flexible battery may include: an electrode assembly having one or more unit cells each of the unit cells including a pair of electrode plates having different polarities, a separator interposed between the respective electrode plates and electrode tabs that protrude from the respective electrode plates; a pair of electrode leads connected to electrode tabs; and a strengthening tab fixed on any one electrode lead connection tab among the electrode tabs.

TECHNICAL FIELD

The present disclosure relates to a flexible battery having a jointstrengthening structure between an electrode tab and an electrode lead.

BACKGROUND

A secondary battery refers to a battery, which can be charged anddischarged, as opposed to a primary battery which cannot be charged, andhas been widely used in the field of advanced electronic devices such ascellular phones, notebook computers, camcorders, and the like. The formfactor of such electronic devices is becoming lighter, if not smaller,all the while performance is improving. Add to those advancements in thedevelopment and implementation of the Internet of Things (IoT), andsecondary batteries as power supplies take on greater importance.

Lithium secondary batteries have a higher voltage than nickel-cadmiumbatteries or nickel-hydrogen batteries, which are mainly used as powersupplies for portable electronic devices and also have a high energydensity per unit weight. Therefore, demand for lithium secondarybatteries is increasing.

A secondary battery typically utilizes an electrochemical reactionoccurring between an electrolyte and a positive electrode and a negativeelectrode when the positive electrode and the negative electrode areconnected to each other when inserted into the electrolyte. Unlikeconventional primary batteries, a secondary battery can be recharged bya charger and used again.

Typically, a lithium secondary battery includes a jelly-roll typeelectrode assembly in which a separator is inserted between a positiveelectrode plate and a negative electrode plate and is then spirallywound together; or includes a flexible stacked type electrode assemblyin which multiple positive electrode plates and negative electrodeplates are stacked with a separator interposed therebetween. Forexample, a cylindrical battery may be manufactured by housing thejelly-roll type electrode assembly in a cylindrical can, injecting anelectrolyte therein, and sealing the can; and a prismatic battery may bemanufactured by pressing the jelly-roll type electrode assembly or thestacked type electrode assembly to be flat and then housing the flatelectrode assembly in a prismatic can. Further, a pouch type battery maybe manufactured by packing the jelly-roll type electrode assembly or thestacked type electrode assembly together with an electrolyte in a pouchtype case. In such an electrode assembly, a positive electrode tab and anegative electrode tab may be withdrawn from a positive electrode plateand a negative electrode plate, respectively, to the outside of theelectrode assembly and then connected to a positive electrode and anegative electrode of a secondary battery.

Meanwhile, an electrode tab on multiple positive electrode plates andnegative electrode plates stacked in a vertical direction may beconnected to an electrode lead. A conventional joint structure betweenan electrode tab and an electrode lead slightly decreases in coherenceduring direct welding. Thus, when a battery is bent during use, aproblem occurs in the joint between the electrode tab and the electrodelead.

According to conventional technologies, when a battery assembly is bent,compressive stress is applied to an inner bent portion and tensilestress is applied to the opposite side. Therefore, a case that covers anelectrode assembly of the battery also expands or contracts, thusincurring mechanical damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an example configuration of an electrodeassembly included in a flexible battery, according to the presentdisclosure.

FIG. 2 is an exploded view of the example configuration of an electrodeassembly of FIG. 1.

FIGS. 3A-D illustrate an example process producing a backing andstrengthening structure using a strengthening tab between an electrodelead connection tab and an electrode lead, in accordance with at leastone embodiment disclosed herein.

FIG. 4 shows different sizes of a strengthening tab added on anelectrode lead connection tab, in accordance with at least oneembodiment disclosed herein.

FIG. 5 shows different sizes of a tab-lead joint portion with anelectrode lead joined on an electrode lead connection tab, in accordancewith at least one embodiment disclosed herein.

FIG. 6 shows different shapes of a strengthening tab added between anelectrode lead connection tab and an electrode lead on a flexiblebattery, in accordance with various embodiments disclosed herein.

FIGS. 7A-D illustrate a process of joining on an electrode leadconnection tab by using an electrode lead bending structure, accordingto various embodiments disclosed herein.

FIG. 8 shows different sizes of an electrode lead portion joined on anelectrode lead connection tab, in accordance with various embodimentsdisclosed herein.

FIG. 9 shows different materials of an electrode lead connection tab andan electrode lead, in accordance with various embodiments disclosedherein.

FIG. 10 illustrates a flexible battery including an electrode assemblyand a case covering the electrode assembly, in accordance with at leastone embodiment disclosed herein.

FIG. 11 illustrates a pattern of upper stamping sections and lowerstamping sections formed in a direction parallel to the width of a caseincluded in a flexible battery, in accordance with at least oneembodiment disclosed herein.

FIG. 12 illustrates different shapes of upper stamping sections andlower stamping sections formed in a case, in accordance with variousembodiments disclosed herein.

FIG. 13 illustrates deformation occurring inside/outside of a case whena flexible battery is bent, in accordance with at least one embodimentdisclosed herein.

FIG. 14 illustrates that a tab-lead joint portion including a backingand strengthening joint structure between an electrode lead connectiontab and an electrode lead and an electrode lead bending structure isinserted into an electrode assembly and electrodes are aligned, inaccordance with at least one embodiment disclosed herein.

FIG. 15 shows a comparison between a battery that includes an electrodeassembly in which a tab-lead joint portion is inserted and electrodesare aligned at the same time, in accordance with at least one embodimentdisclosed herein, and a battery that does not include the electrodeassembly.

FIG. 16 illustrates an example embodiment of an electrode plate includedin an electrode assembly to insert a tab-lead joint portion including abacking and strengthening joint structure and an electrode lead bendingstructure into the electrode assembly, as disclosed herein.

FIG. 17 shows a comparison between the results of bending tests beforeand after a tab-lead joint portion that includes a backing andstrengthening joint structure and an electrode lead bending structure isinserted into an electrode assembly.

DETAILED DESCRIPTION

The embodiments described, recited, and even contemplated herein providea stable flexible battery that has a strengthening tab formed as a metalplate of a predetermined thickness placed between an electrode lead andan electrode lead connection tab that is included in an electrodeassembly. An end of the electrode lead may be bent 180° in a directionopposite toward the outside of the electrode assembly while it is weldedon the electrode lead connection tab, thus electrochemical propertiesmay be maintained by minimizing a local mechanical load caused bybending of the flexible battery.

A flexible battery assembly according to the present disclosure mayinclude: at least: an electrode assembly that may be equipped with oneor more unit cells, each of the unit cells including a pair of electrodeplates having different polarities, a separator interposed between therespective electrode plates, and electrode tabs protruding from therespective electrode plates but not coated with an electrode mixture; astrengthening tab welded and fixed on any one electrode lead connectiontab among the electrode tabs included in the electrode assembly; and apair of electrode leads welded on the strengthening tab and the otherelectrode lead connection tab, respectively. Either electrode lead ofthe pair of electrode leads may be welded on the strengthening tab,which is added between the electrode lead connection tab and theelectrode lead and connected to the electrode lead connection tab.Either electrode lead of the pair of electrode leads may be bent in adirection toward the outside of the electrode assembly from a directiontoward the inside of the electrode assembly.

A tab-tab joint portion may include electrode plates having the samepolarity electrically connected in parallel to each other through anelectrode parallel connection tab, and the tab-tab joint portion may betaped on a separator that covers an outer surface of the outermostelectrode plate placed on the uppermost or lowermost end of theelectrode assembly.

The flexible battery may further includes a case that has upper stampingsections and lower stamping sections repeatedly stamped to surround theoutside of the electrode assembly. The multiple upper stamping sectionsand lower stamping sections are successively formed in a directionparallel to the width of the electrode assembly and the case.

A tab-lead joint portion that is backed and strengthened using thestrengthening tab and is located between the electrode lead connectiontab and the electrode lead may be inserted into the electrode assembly,and a tab-lead joint portion that includes an electrode lead bendingjoint structure may be inserted in the electrode assembly.

The electrode plates included in the electrode assembly may include afirst electrode plate E1 that includes the electrode lead connection taband the electrode parallel connection tab on opposing sides and a secondelectrode plate E2 that includes only the electrode parallel connectiontab on one side, and an electrode mixture may be coated on the secondelectrode plate E2 to cover the electrode lead connection tab of thefirst electrode plate E1.

According to the embodiments described, recited, and contemplatedherein, it is possible to implement a stable flexible battery having astructure in which a strengthening tab that is formed as a metal plateof a predetermined thickness may be placed between an electrode lead andan electrode lead connection tab that is included in an electrodeassembly, and an end of the electrode lead may be bent 180° in adirection opposite toward the outside of the electrode assembly while itis welded on the electrode lead connection tab. Thus, electrochemicalproperties may be maintained by minimizing a local mechanical loadcaused by bending of the flexible battery.

Embodiments of a flexible battery are described, recited, and suggestedherein with reference to the accompanying drawings.

The following exemplary embodiments are provided only for understandingof the present disclosure but not intended to limit the right scope ofthe present disclosure. Therefore, embodiments that perform the samefunctions in the same scope as those presently disclosed and recited arealso included in the right scope of the present disclosure.

Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Whenreference numerals refer to components of each drawing, although thesame components are illustrated in different drawings, the samecomponents are referred to by the same reference numerals as possible.Further, if it is considered that description of related knownconfiguration or function may cloud the gist of the present disclosure,the description thereof will be omitted.

Further, in describing components of the present disclosure, terms suchas first, second, A, B, (a), (b), etc. can be used. These terms are usedonly to differentiate the components from other components. Therefore,the nature, order, sequence, etc., of the corresponding components arenot limited by these terms. It is to be understood that when one elementis referred to as being “connected to” or “coupled to” another element,it may be directly connected or coupled to another element or beconnected or coupled to another element, having still another element“connected” or “coupled” therebetween.

FIG. 1 illustrates an example configuration of an electrode assemblyincluded in a flexible battery, according to the present disclosure; andFIG. 2 is an exploded view of the example configuration of an electrodeassembly of FIG. 1.

An electrode assembly 100 includes unit cells, each including a negativeelectrode plate 10 and a positive electrode plate 20 with a separator 30interposed therebetween, an electrolyte serving as an ion transportmedium between negative electrode plate 10 and positive electrode plate20, and electrode tabs 12, 14, 22 and 24 protruding from the electrodeplates 10 and 20 may be used to implement electrode parallel connectionand as an electrode lead connection, depending on the application. Anyone or more of the electrode plates including the negative electrodeplate 10 and the positive electrode plate 20 may be equipped on bothsides with an electrode parallel connection tab and an electrode leadconnection tab spaced apart from each other. For example, a negativeelectrode plate 10 placed on the lowermost end of the electrode assembly100 may be equipped with a negative electrode parallel connection tab 12and a negative electrode lead connection tab 14, and a positiveelectrode plate 20 placed on the opposite side of the separator facingthe negative electrode 10 may be equipped with a positive electrodeparallel connection tab 22 and a positive electrode lead connection tab24.

One or both of the top and bottom surfaces of each electrode plateserving as a current collector may be coated with an electrode mixture,and the electrode parallel connection tabs and the electrode leadconnection tabs protrude from the electrode plates. The electrodeparallel connection tabs and the electrode lead connection tabs may beexposed without being coated with the electrode mixture.

The multiple electrode plates having the same polarity may be connectedto each other through an electrode parallel connection tab. That is,multiple negative electrode plates 10 and multiple positive electrodeplates 20 are electrically connected in parallel to each other forming atab-tab joint portion connecting electrode tabs 12 and 22. The electrodeassembly may be electrically connected through the electrode leadconnection tab 14 and 24 to an electrode lead 60 exposed to the outsideof a case. The separator 30 physically separates the electrode plates,but allows ions contained in the electrolyte to pass through.

As for the negative electrode plates placed on the uppermost end and thelowermost end of the electrode assembly, only one surface of eachnegative electrode plate may be coated with a negative electrodemixture.

Electrode parallel connection tab 12 or 22 protruding from negativeelectrode plate 10 or positive electrode plate 20 electrically connectselectrode plates having the same polarity in parallel to each other.Tab-tab joint portions connected in parallel to each other are locatedon the separator covering an outer surface of the outermost electrodeplate placed and taped on the uppermost end or the lowermost end of theelectrode assembly.

FIGS. 1 and 2 show a tab-tab joint portion where electrode parallelconnection tabs 12 and 22 on the electrode plate are connected inparallel to each other and a tab-lead joint portion where the electrodelead connection tabs 14 and 24 and the electrode lead are connected toeach other. The tab-tab joint portion and the tab-lead joint portion areelectrically connected and joined to each other by any one of spotwelding, laser welding, or a conductive adhesive.

FIGS. 3A-D illustrate an example process producing a backing andstrengthening structure using a strengthening tab between an electrodelead connection tab and an electrode lead, in accordance with at leastone embodiment disclosed herein. FIG. 3A shows a separate strengtheningtab 50 added to electrode lead connection tabs 14 and 24 that are placedon one side of the electrode assembly of FIGS. 1 and 2. Strengtheningtab 50 may be joined to an electrode lead 60. Thus, a backing structurefor the electrode lead connection tabs 14 and 24 and the electrode lead60 may be formed using the strengthening tab 50. The strengthened jointmethod for electrode lead connection tabs 14 and 24 and the electrodelead 60 may be applied to at least any one of a positive electrode taband a negative electrode tab.

FIG. 3A shows that, among multiple electrode plates included in anelectrode assembly, an electrode equipped with an electrode leadconnection tab may protrude to one side of the electrode assembly to bejoined to strengthening tab 50, which may be formed of a metal material.

FIG. 3B shows that strengthening tab 50 may be joined on the electrodelead connection tab 14.

FIG. 3C shows that the electrode lead 60 may be prepared to be joined onthe electrode lead connection tab 14 on which the strengthening tab 50is added.

FIG. 3D shows that the electrode lead 60 may be joined on the electrodelead connection tab 14 on which the strengthening tab 50 is added.

FIG. 4 shows different sizes of a strengthening tab added on anelectrode lead connection tab, in accordance with at least oneembodiment disclosed herein. As shown, the strengthening tab 50 added onthe electrode lead connection tab 14 reinforces the strength of a jointportion between the electrode lead connection tab 14 and the electrodelead 60 and thus physically strengthens the joint portion.

On an upper end of the electrode lead connection tab 14 and 24 extendedfrom the electrode plate 10 and 20 of the electrode assembly, thestrengthening tab 50 formed of a homogeneous or heterogeneous metal andhaving a thickness one to three times greater than the electrode leadconnection tab is added by backing and welded. The strengthening tab 50added by backing and the electrode lead connection tab 14 and 24 mayhave the same thickness or different width.

The added strengthening tab 50 may have a width of 3 mm to 5 mm and alength of 2 mm to 4 mm. However, this is just an example and the presentdisclosure is not limited thereto.

FIG. 5 shows different sizes of a tab-lead joint portion with anelectrode lead joined on an electrode lead connection tab, in accordancewith at least one embodiment disclosed herein. As shown, the electrodelead 60 assembled on the strengthening tab 50 added by backing andjoined to the electrode lead connection tab may have a width of, e.g., 2mm to 3 mm and a length of, e.g., 0.5 mm to 1 mm. However, this is justan example and the present disclosure is not limited thereto. Theelectrode plates in the present disclosure may be any one of a groupconsisting of aluminum, stainless steel and copper, and the electrodelead may be formed of any one material of a group consisting ofaluminum, nickel, and nickel-coated copper.

FIG. 6 shows different shapes of a strengthening tab added between anelectrode lead connection tab and an electrode lead on a flexiblebattery, in accordance with various embodiments disclosed herein. Asdepicted, the strengthening tab 50 added by backing on the tab-leadjoint portion for the electrode lead connection tab 14 and 24 and theelectrode lead 60 may be formed into any one shape of a group consistingof a circular shape, an oval shape, and a polygonal shape.

FIGS. 7A-D illustrate a process of joining on an electrode leadconnection tab by using an electrode lead bending structure, accordingto various embodiments disclosed herein. As depicted, electrode lead 60may be joined to electrode lead connection tabs 14 and 24 on one side ofthe electrode assembly.

While electrode lead 60 may be placed in parallel above the electrodelead connection tabs 14 and 24, a part of an end of the electrode lead60 may be welded on upper ends of the electrode lead connection tabs 14and 24 (FIG. 7A). In this state, the electrode lead 60 may be bent 180°,thus electrode lead 60 may be bent from the electrode lead connectiontabs 14 and 24 toward the outside of the electrode assembly (FIG. 7B-D).

This method of connecting the electrode lead connection tabs 14 and 24and the electrode lead 60 by bending may be applied to at least any oneof a positive electrode tab and a negative electrode tab.

FIG. 8 shows different sizes of an electrode lead portion that may bejoined on an electrode lead connection tab, in accordance with variousembodiments disclosed herein. As depicted, a joint portion of theelectrode lead 60 that may be joined to the upper end of the electrodelead connection tab extended from the electrode plate of the electrodeassembly may have a width of, e.g., 2 mm to 3 mm and a length of, e.g.,1 mm to 3 mm. The joint portion may have an optimal length of 1.5 mm.However, this is just an example and the present disclosure is notlimited thereto.

FIG. 9 shows different materials of an electrode lead connection tab andan electrode lead, in accordance with various embodiments disclosedherein. As depicted, the electrode plates may be any one of a groupconsisting of aluminum, stainless steel and copper, and the electrodelead may be formed of any one material of a group consisting ofaluminum, nickel, or nickel-coated copper.

FIG. 10 illustrates a flexible battery including an electrode assemblyand a case covering the electrode assembly, in accordance with at leastone embodiment disclosed herein. As depicted, a case 200 having astructure in which upper stamping sections and lower stamping sectionsare alternatively repeated is placed to surround the outside of theelectrode assembly according to the present disclosure.

FIG. 11 illustrates a pattern of upper stamping sections and lowerstamping sections formed in a direction parallel to the width of a caseincluded in a flexible battery, in accordance with at least oneembodiment disclosed herein. As depicted, the multiple upper stampingsections 212 and 222 and lower stamping sections 214 and 224 repeatedlystamped on the case have a repeated pattern and shape and thus cancompress and tension the flexible battery including the electrodeassembly during bending, twisting, or crumpling.

The multiple upper stamping sections 212 and 222 and lower stampingsections 214 and 224 may be successively formed in a direction parallelto the width of the electrode assembly and the case.

The multiple upper stamping sections 212 and 222 and lower stampingsections 214 and 224 may be stamped by an upper mold and a lower mold,respectively.

The case surrounding the outside of the electrode assembly may includean upper case 210 and a lower case 220 on the electrode assembly basedon a dotted line in a sealing portion 230. That is, multiple upperstamping sections 212 and 222 and multiple lower stamping sections 214and 224 repeatedly formed on the case are symmetric with respect to thesealing portion 230 and symmetrically stamped on the upper case 210 andthe lower case 220. In this state, the sealing portion is bent in avertically symmetric manner and then, the electrode assembly may behoused inside the case.

The sealing portion, which may divide the upper case 210 and the lowercase 220, may have a width of, e.g., 3 mm to 5 mm, and a substantivesealing may have a width of, e.g., 1 mm to 2 mm. However, this is justan example and the present disclosure is not limited thereto.

FIG. 12 illustrates different shapes of upper stamping sections andlower stamping sections formed in a case, in accordance with variousembodiments disclosed herein. As shown, a height h of the multiple upperstamping sections repeated on the case may be identical to a height h′of the multiple lower stamping sections repeated on the case (h=h′).

The heights h and h′ of the multiple upper stamping sections and lowerstamping sections repeated on the case may be in the range of, e.g., 0.5mm to 1 mm and have an optimum value of 0.75 mm. However, this is justan example and the present disclosure is not limited thereto.

Further, a width a between peaks of the multiple upper stamping sectionsadjacent to each other on the case may be identical to a width b betweentroughs of the multiple lower stamping sections (a=b), and, thus, a wavepattern is formed.

FIG. 13 illustrates deformation occurring inside/outside of a case whena flexible battery is bent, in accordance with at least one embodimentdisclosed herein. As shown, when the case forming the flexible batteryis applied with external force and deformed to be bent, tensile stressis applied onto the case outside the flexible battery and compressivestress is applied onto the case inside the flexible battery.

Inside the flexible battery, the height h of the repeated upper stampingsections increases to between h to 2h due to the compressive stresscaused by bending, twisting, or crumpling. Outside the flexible battery,the height h of the repeated upper stamping sections decreases tobetween 0 and h due to the tensile stress.

FIG. 14 illustrates that a tab-lead joint portion including a backingand strengthening joint structure between an electrode lead connectiontab and an electrode lead and an electrode lead bending structure isinserted into an electrode assembly and electrodes are aligned, inaccordance with at least one embodiment disclosed herein, multiplestructures employ the method of joining an electrode lead connection taband an electrode lead. That is, a first tab-lead joint portion has astructure in which backing and strengthening is implemented by astrengthening tab added between an electrode lead connection tab and anelectrode lead, and a second tab-lead joint portion has a structure inwhich while a part of an end of the electrode lead is welded on theupper ends of the electrode lead connection tabs 14 and 24, theelectrode lead is bent in the 180° opposite direction toward the outsideof the electrode assembly. FIG. 14 illustrates that the tab-lead jointportion including a backing and strengthening joint structure and anelectrode lead bending joint structure is inserted into the electrodeassembly and then aligned by a tab-tab joint portion.

FIG. 15 shows a comparison between a battery that includes an electrodeassembly in which a tab-lead joint portion is inserted and electrodesare aligned at the same time, in accordance with at least one embodimentdisclosed herein, and a battery that does not include the electrodeassembly.

FIG. 17 shows a comparison between the results of bending tests beforeand after a tab-lead joint portion that includes a backing andstrengthening joint structure and an electrode lead bending structure isinserted into an electrode assembly. As shown, in depiction (on theleft), before the tab-lead joint portion, which may include the backingand strengthening joint structure using the strengthening tab 50 and theelectrode lead bending joint structure, is inserted into the electrodeassembly, breakage occurs on the joint portion between the electrodelead connection tab and the electrode lead in a bending test on theflexible battery.

However, in the depiction (on the right), after the tab-lead jointportion, which may include the backing and strengthening joint structureusing the strengthening tab 50 and the electrode lead bending jointstructure, is inserted into the electrode assembly, there is no breakageon the joint portion between the electrode lead connection tab and theelectrode lead during a bending test on the flexible battery.

FIG. 16 illustrates an example embodiment of an electrode plate includedin an electrode assembly to insert the tab-lead joint portion includingthe backing and strengthening joint structure using the strengtheningtab 50 and the electrode lead bending structure into the electrodeassembly, as disclosed herein.

The electrode plates included in the electrode assembly include a firstelectrode plate E1 including all the electrode lead connection tab andthe electrode parallel connection tab on both sides and a secondelectrode plate E2 including only the electrode parallel connection tabon one side.

As for the first electrode plate E1, a portion coated with the electrodemixture has a horizontal length of W and a vertical length of D and thushas an area of WD. The electrode lead connection tab has a verticallength of D′.

As for the second electrode plate E2, a portion coated with theelectrode mixture has a horizontal length of W and a vertical length ofD+D′ and thus has an area of W(D+D′).

With the above-described structure, the tab-lead joint portion can beinserted into the electrode assembly and aligned at the same time whenthe cell can be driven stably.

Hereafter, a specific example of experimental conditions for theflexible battery including the backing and strengthening joint structureusing the strengthening tab 50 and the electrode lead bending jointstrengthening structure will be described.

A bending test was performed on the flexible battery according to thepresent disclosure with a cylindrical structure of an R20 battery totest bending properties. To be specific, the test was repeated 5000times, and the flexible battery was confirmed as having a capacityretention of 90% or more.

A specific operating environment is as shown in the following Table 1.

TABLE 1 Nominal Capacity (mAh)  50 Energy Density (Wh/L) 114 NominalVoltage 3.8 V Charging Voltage 4.35 V Operating Temp. −10~35° C. StorageTemp. −20~45° C. Size Width 16 ± 0.5 mm Thickness 2 ± 0.2 mm Length 52 ±1.0 mm

The present disclosure makes it possible to implement a stable flexiblebattery in which a strengthening tab formed as a metal plate having apredetermined thickness is placed between an electrode lead and anelectrode lead connection tab included in an electrode assembly when theelectrode lead and the electrode lead connection tab are assembled andan electrode lead bending joint structure is combined, and, thus,electrochemical properties can be maintained by minimizing localmechanical load caused by bending of the flexible battery.

We claim:
 1. A flexible battery, comprising: an electrode assemblyhaving one or more unit cells, each of the unit cells including: a pairof electrode plates having different polarities, a separator interposedbetween the respective electrode plates, and electrode tabs thatprotrude from the respective electrode plates; a pair of electrode leadsconnected to electrode tabs; and a strengthening tab fixed on any oneelectrode lead connection tab among the electrode tabs.
 2. The flexiblebattery of claim 1, wherein either electrode lead of the pair ofelectrode leads is fixed to the strengthening tab, which is addedbetween the electrode lead connection tab and the electrode lead andconnected to the electrode lead connection tab.
 3. The flexible batteryof claim 1, wherein either electrode lead of the pair of electrode leadsis bent in a direction toward the outside of the electrode assembly froma direction toward the inside of the electrode assembly.
 4. The flexiblebattery of claim 1, wherein an electrode parallel connection tab amongthe electrode tabs connects electrode plates having the same polarityamong multiple stacked electrode plates.
 5. The flexible battery ofclaim 4, wherein a tab-tab joint portion at which the electrode plateshaving the same polarity are electrically connected in parallel to eachother through the electrode parallel connection tab is disposed on aseparator covering an outer surface of the outermost electrode plateplaced on the uppermost end or the lowermost end of the electrodeassembly.
 6. The flexible battery of claim 1, wherein a tab-lead jointportion at which the electrode lead connection tab and the electrodelead connected together is located inside of the electrode assembly. 7.The flexible battery of claim 6, wherein the electrode plates include afirst electrode plate having electrode lead connection tab and theelectrode parallel connection tab on opposing sides and a secondelectrode plate having only the electrode parallel connection tab on oneside, and an electrode mixture is coated on the second electrode plateto overlap the electrode lead connection tab of the first electrodeplate.
 8. The flexible battery of claim 1, further comprising: a case inwhich upper stamping sections and lower stamping sections are repeatedlyformed, surrounding the outside of the electrode assembly.
 9. Theflexible battery of claim 8, wherein the multiple upper stampingsections and lower stamping sections are successively formed in adirection parallel to the width of the electrode assembly and the case.